/**
 * Copyright 2009-2020 the original author or authors.
 * <p>
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * <p>
 * http://www.apache.org/licenses/LICENSE-2.0
 * <p>
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.ibatis.builder.annotation;

import org.apache.ibatis.builder.BuilderException;

import java.lang.reflect.Method;
import java.util.Arrays;
import java.util.List;
import java.util.stream.Collectors;

/**
 * The interface that resolve an SQL provider method via an SQL provider class.
 *
 * <p> This interface need to implements at an SQL provider class and
 * it need to define the default constructor for creating a new instance.
 *
 * @since 3.5.1
 * @author Kazuki Shimizu
 */
public interface ProviderMethodResolver {

	/**
	 * Resolve an SQL provider method.
	 *
	 * <p> The default implementation return a method that matches following conditions.
	 * <ul>
	 *   <li>Method name matches with mapper method</li>
	 *   <li>Return type matches the {@link CharSequence}({@link String}, {@link StringBuilder}, etc...)</li>
	 * </ul>
	 * If matched method is zero or multiple, it throws a {@link BuilderException}.
	 *
	 * @param context a context for SQL provider
	 * @return an SQL provider method
	 * @throws BuilderException Throws when cannot resolve a target method
	 */
	default Method resolveMethod(ProviderContext context) {
		List<Method> sameNameMethods = Arrays.stream(getClass().getMethods())
				.filter(m -> m.getName().equals(context.getMapperMethod().getName()))
				.collect(Collectors.toList());
		if (sameNameMethods.isEmpty()) {
			throw new BuilderException("Cannot resolve the provider method because '"
					+ context.getMapperMethod().getName() + "' not found in SqlProvider '" + getClass().getName() + "'.");
		}
		List<Method> targetMethods = sameNameMethods.stream()
				.filter(m -> CharSequence.class.isAssignableFrom(m.getReturnType()))
				.collect(Collectors.toList());
		if (targetMethods.size() == 1) {
			return targetMethods.get(0);
		}
		if (targetMethods.isEmpty()) {
			throw new BuilderException("Cannot resolve the provider method because '"
					+ context.getMapperMethod().getName() + "' does not return the CharSequence or its subclass in SqlProvider '"
					+ getClass().getName() + "'.");
		} else {
			throw new BuilderException("Cannot resolve the provider method because '"
					+ context.getMapperMethod().getName() + "' is found multiple in SqlProvider '" + getClass().getName() + "'.");
		}
	}

}
